50 ON IRREGULARITY IN THE GROWTH OF SALMON. [Jan. 13, 
of Professor Agassiz’s * expressions (himself adverse to the transmuta- 
tion theory) cannot be denied. In treating of the relations between 
animals and plants and the surrounding world, he says, ‘ And yet, 
without a thorough knowledge of the habits of animals, it will never 
be possible to ascertain with any degree of precision the true limits 
of all those species which descriptive zoologists have of late admitted 
with so much confidence into their works. And, after all, what does 
it matter to science that thousands of species, more or less, should 
be described and entered into our systems if we know nothing about 
them!” . . .‘*Then we may learn with more precision how far the 
species described from isolated specimens are founded in nature, or 
how far they are only a particular stage of growth of other species ; 
then we shall know, what is yet too little noticed, how extensive the 
range of variation is among animals observed in their wild state, 
or rather, how much individuality there is in each and all living 
beings.” 
No decided answer can be given to the questions at issue while so 
much of the commoner facts in the life-history of the Salmonidee 
are conjectural. Every scrap of information based on accurate ob- 
servations is needed to unravel the phenomena, whether dependent 
on reasons physiological or physical, teleological or pangenetical. 
EXPLANATION OF PLATE II. 
Ntustrations of the variable growth of Salmonoids in tanks of fresh water. 
Fig. 1. Young of the Great-Lake Trout (Salmo lacustris?), being one among 
others reared from a batch of ova from Huningue, near Basle, and 
presented to the Society by Mr. Frank Buckland, 9th or 10th March, 
1869. The specimen was nine months old, haying been hatched about 
the middle of March; and the drawing was taken immediately after 
death, on the 15th December, 1869, natural size, 7. e. 3°3 inches long. 
A few of the same brood were somewhat larger, others smaller. 
Fig. 2. A young Salmon (?) from Rhine ova, received as above. Length 1-95 inch ; 
natural dimensions: sketched 14th December, 1869. 
Fig. 3. Another specimen of the same batch of Salmon (?), and corresponding 
to fig, 2 in age, viz. about 9 months. Natural size, =2°7 inches, and, 
as in fig. 1, figured immediately after death. 
The brackets, respectively lettered a, 6, between the preceding figures, 
indicate the length (3:1 inches) of one of nine good-sized specimens of 
the same brood of Salmon (?), which died on the 6th October, or some- 
where betwixt 6 and 7 months old. Had they lived until the middle 
of December, doubtless they would have grown as large as the Great- 
Lake Trout here represented. 
Fig. 4. Salmon (?) from Rhine ova, fully 2 years old, which, like the above, was 
reared and retained in the Society’s freshwater aquarium at the Re- 
gent’s Park. Hatched February 1866, died 14th April, 1868. 
The figure, natural size and colour, taken immediately after death, 
shows the assumption of the silvery Smolt-coat, indicative of the mi- 
gratory impulse. 

* An Essay on Classification (London, 1859), pp. 85, 86. 
